1. Field of the Invention
The present invention relates to the solubilization of solvent resistant polymers to form an article. More specifically, the present on relates to a process to solubilize poly(phenylene sulfide) (PPS) at elevated temperatures using high boiling organic solvents which are solids at ambient temperature, and to form a useful article of PPS.
2. Description of Related Art
Crystalline poly(phenylene sulfide) is a very useful high temperature polymeric material. The properties of commercially available PPS include:
1 A relatively high glass transition temperature of about 85.degree.-150.degree. C., PA1 2. A very high crystallized melting point of about 286.degree. C., PA1 3. Thermal stability, and PA1 4. High solvent resistance. PA1 A. contacting poly(phenylene sulfide) with at least one organic compound, consisting essentially of carbon and hydrogen and optionally oxygen, nitrogen, sulfur, halogen, or mixtures of these atoms, said at least one organic compound having a molecular weight of between about 160 and 450 daltons and having at least one six membered aromatic ring structure, which compound is a stable liquid at a temperature of between about 240.degree. and 400.degree. C. at ambient pressure, at a temperature of between about 240.degree. and 400.degree. C. at ambient pressure for a time effective to dissolve greater than about 10% by weight of the poly(phenylene sulfide) present, with the proviso that when oxygen is present, the organic compound is not diphenyl oxide or substituted diphenyl oxide; PA1 B. forming the solution of poly(phenylene sulfide) and the organic compound of Step (A) into a desired article configuration; PA1 C. removing the at least one organic compound; and PA1 D. recovering the article comprising poly(phenylene sulfide) formed thereby. PA1 (A) contacting poly(phenylene sulfide) with: PA1 (B) forming the solution of poly(phenylene sulfide) and the organic compound of Step (A) into a desired article configuration; PA1 (C) removing the at least one organic compound; and PA1 (D) recovering the article comprising poly(phenylene sulfide) formed thereby.
Unfortunately, these properties make PPS a very difficult polymer to mold into desireable useful shaped articles.
The thermal stability and solvent resistance make PPS an ideal candidate for ultrafiltration membranes, hollow fibers, solid fibers and the like. However, the very useful thermal and solvent resistance of PPS presents severe problems in shaping the polymer into a desired form.
Formation of articles of manufacture from PPS requires special solvents for the polymers.
Most of the art provides for simple relatively low boiling solvents which were used to dissolve the reactants used to prepare the PPS from the monomers. Once PPS is formed, it usually separates from the polymerization solvent(s).
Poly(phenylene sulfide) is generally regarded as being insoluble in most common solvents. A number of hot aprotic polar organic compounds, peralkylated cyclic ureas, or N-alkylactams such as N-methyl-2-pyrrolidinone, or N,N-diethylbenzamide, N,N-diethyltoluamide, N,N-dimethylethylene urea, dimethylacetamide, hexamethylphosphoramide or N-methylcaprolactam as described as "solvents" in the synthesis of PPS. It appears that these organic compunds are solvents (or dispersants and/or heat transfer agents) for the reactants and from which the PPS precipitates after formation.
H. A. Hill in U.S. Pat. No. 4,118,363 discloses that PPS is a difficult polymer to solubilize, and that diphenyl oxide has been used as a high boiling solvent at elevated temperatures. Further, Hill discloses that alkyl substituted and halogen substituted diphenyl oxides have also been used to solubilize PPS.
Strongly acidic hot materials, such as concentrated sulfuric acid, chlorosulfonic acid, and trifluoromethylsulfonic acid, are suggested as solvents for PPS. However, these materials may react with the aromatic portion of the polymer forming an acid derivative which has properties completely different than PPS, and the derivative then "dissolves" in the hot solvent.
J. Kawabata et al., in Japanese Kokai patent application No. 59-120779 (June 14, 1984) (Kokai No. 01-432) disclose the use of poly(phenylene sulfide) as a composite film for use in gas separation.
Poly(phenylene sulfide) as a polymer is described in detail by H. W. Hill, Jr. and D. G. Brady in "Poly(phenylene sulfide)" in Kirk-Othmer Encyclopedia of Chemical Technology, 3rd Ed., Vol. 18, P. 793-814 (1982), which is incorporated herein by reference.
None of the above references teach or suggest the present invention in the use of high boiling solvents comprising organic compounds which are solids at ambient temperature, to solubilize poly(phenylene sulfide), forming the solubilized poly(phenylene sulfide) into the shape of an article of manufacture, removing the organic compound, and recovering the useful article of poly(phenylene sulfide).